Wombat,
This is great news!
When it comes to an agent, remember you are hiring them and not the other way around. If they're both open to representing you, it is completely legit to 1) let each of them know this, and 2) ask them for a couple references of other authors they represent and to then call these folks to gage their general satisfaction. If they balk at this, they're either messed up ego-wise or have something to hide, and that should be a flashing red light. It would also be useful to ask each of them which publishers they'll be targeting with your book (then look into these publishers to ensure you like what they do too), their track record of getting work published with said publishers, and any info they can share about their overall success rate with getting work published. Other than that, you'll want to check into what sort of cut they'll be taking and if it is standard. You likely have a local writers collective of some sort, and if so you should join if you haven't already - they will likely be able to advise you as to this and also provide additional support. Also, they'll likely have the inside goods on these agents and may have had experiences with them that authors provided as reference wouldn't likely share.